You still have to give the exceptions a rating. Which means there needs to be a category to hold that rating. So you might as well give it every player.
As far as simulation what doesn't happen in the NFL - why doesn't it make sense?
Does Ray Rice throw halfback passes in the NFL? No because that's not in Baltimore's game plan. However, if he's on a team in Madden that DOES have a halfback pass in their playbook, and that team has Ray Rice, or any other HB that doesn't throw passes in the NFL, and that team calls a HB pass and the HB throws the ball - how does the game resolve that?
Exceptions wouldn't cut it. What if I don't have one of the exceptions, but call the play? Should it be an automatic failure? Is that realistic?
To me, ratings mattering is making it so I can have a player that's a 1 at something do that something, and fail misearbly. Otherwise, you've got the P blocking a DT.
To me, it doesn't matter if P's play OL in the NFL once the simulation/gameplay engine comes into play. That should be reflected in the ratings (Ps should have 1's in blocking) and then the result of those ratings gets played out. (1 PBS vs 80 BSH and 80 PMV, for example).
The CBs should have a weak RTE and RLS rating. That doesn't mean they should be totally incapable of running 20 feet forward, turning to the middle of the field, and then running 20 feet forward. That's all an in-route is.
Whether or not he succeeds at doing that vs press coverage would be determined by his RLS rating. How precisely he runs that route depends on his RTE (I wouldn't throw this to him if I needed 10 yards and that was a 10 yard route - he might run it at 7 yards and then not read the coverage right, etc).
There's a difference between "not able to run a route well against press coverage" and "running diagonally and having the ball hit him in the side of the helmet"
Oh and as far as why has STR when you have blocking strength:
RBS/PBS = Hold long they engage the block. STR could equal how much push you get. A low STR o-lineman with high RBS could be one that holds his block forever, but doesn't drive the D-lineman 3 yards off the LOS.
RTE is for running precise routes. I.e. the WR knows where to be and when to be there. AGI could impact how square his cuts are and how fast he makes them and how much speed he loses in and out of those cuts, and how well he can shake his man in man-to-man coverage. A high AGI WR could be more adept at throwing the fake in a double move route, for example.
Those are different skills/physical traits. No problems with having those, imo.